[rdl]

For the past 12 years I have often been either the only American in a group, or the only white guy, or the only person who went to a top-tier tech school. I've been in groups that have been totally multicultural, or groups where one other ethnicity or race predominated. (admittedly, everything has been at most 30% female).

I really haven't observed ethnicity or race as a primary factor in team dynamics. Even first language, assuming people have a minimal level of fluency, hasn't been a major factor; even with my minimal French, I've ended up hanging out with French video gamers and sci fi fans (all 3 of them at a big base; they spoke maybe 100 words of English) vs. a bunch of other Americans.

Volitional things like the kind of music you like, the job you do, your hobbies, etc. are really a much bigger factor, at least in my limited experience, than race or ethnicity.